Mud pump piston



Sept 1942' E. E. MILLER 2 295,678

MUD PUMP PISTON Filed March 17, 1941 j w wmlaw by the mud pump liner.

Patented Sept. 15, 1942 UNITED STATS iF-ATENT QFFICE MUD PUMP PISTONErwin E. lVIiller, Fullerton, Calif.

Application March 17, 1941, Serial No. 383,745

1 Claim.

This invention relates to improvements in mud pump pistons, and may beregarded as a further development of the invention disclosed in mycopending application Serial No. 321,061, filed February 27, 1940.

In the above-mentioned application I'have disclosed a mud pump pistonformed of a onepiece body which fills the major portion of thecross-sectional area of the cylinder of the mud pump in which the pistonis to be installed. On the periphery of this body there is a centralflange of suflicient external diameter as to substantially flt againstthe cylinder walls afforded On both sides of the central flange thereare a series of small perforated flanges and rubber or similar materialis molded around and between these flanges and through the perforationstherein. The rubber provides flexible lips at the ends of the piston andprovides cylinder-wall engaging surfaces of the piston on opposite sidesof the central flange.

The central flange on the body which engaged the cylinder walls affordedby the mud pump liner was heretofore regarded as being necessarilypresent when the piston was subjected to high pressure conditions inthat it prevented the rubber from being forced longitudinally around thebody of the piston. Its presence was known to be objectionable in thatthere was a i tendency for the rubber to be squeezed around the edge ofthe central flange during reciprocation of the piston so that adjacentthe flange the rubber in the course of time became chewed away andsometimes loosened therefrom. Ala.

though such objections were present the presence of the flange wasthought to be required in order to keep the major portion of the rubberin place. Other objections to the central flange were that if sandworked between the flange and the liner scoring of the liner was apt tooccur.

I have found that the central flange on the piston can be omittedentirely in a mud pump piston or this character and that a highlysuccessful piston can be produced which can be used under extremely highpressures if the body of the piston is made adequately large so as tohave a relatively thin layer of rubber on its exterior which isadequately anchored to the body of the piston. In this way the exteriorof the rubber forms the entire cylinder-wall engaging surface of thepiston and eliminates the chewing away of rubber adjacent the centralflange, the loosening of the rubber adjacent the central flange, and thedanger of scoring. The layer of rubber on the exterior of the pistonmust not only be adequately anchored to the body of the piston but mustbe relatively thin as compared with the size of the piston body so thatno large mass of rubber is present on which the high pres- 5 es canbecome effective to materially distort it and loosen it from the body ofthe piston.

With the foregoing and other objects in view, which will be mademanifest in the following detailed description and specifically pointedout in the appended claim, reference is had to the accompanying drawingfor an illustrative embodiment of the invention, wherein:

Figure 1 is a vertical section through the improved mud pump pistonembodying the present invention illustrated as positioned within a mudpump liner, the liner being indicated by dotted lines;

Fig. 2 is a View in end elevation of the piston shown in Fig. 1, partsof the rubber being shown as having been removed; and

Fig. 3 is a partial View in side elevation of the body of the piston.

Referring to the accompanying drawing wherein similar referencecharacters designate similar parts throughout, the improved pistoncomprises a one-piece body I!) which may be formed of steel or othermetal. This body has a longitudinal bore I! therethrough which may beeither cylindrical as shown, or tapered, depending upon the constructionof the piston rod of the pump in which the piston is to be installed.

The body l0 occupies the major portion of the cross-sectional area ofthe cylinder the walls of which are provided by the conventional linerindicated in dotted lines at L The body I!) is of generally cylindricalform and has a series of substantially equally spaced. grooves l2 turnedor otherwise formed therein deflning'a series of substantially equallyspaced flanges I3. These flanges are relatively shallow as compared withthe diameter of the piston body. They are longitudinally perforated asindicated by the aligned perforations l4. Rubber or similar compositionindicated at I5 is molded around these flanges and between them and inthe perforations [4 after which it is vulcanized or cured directly tothe body.

As will be noted from an inspection of Fig. 1, the rubber forms theentire cylinder-wall engaging surface of the piston. At the ends of thepiston the rubber may be flared outwardly to provide lips l6 which aresomewhat flexible and which are designed to wipe closely against thecylinder walls. These lips normally expand outwardly but on insertion ofthe piston into the liner they must be contracted slightly from thepositions shown.

On the end faces of the piston there are preferably formed or cutgrooves l1 and I8 disposed at right angles to each other in which theend portions of the rubber are molded. If desired the rubber may beextended out over the hubs of the piston as indicated at l9 and ifdesired, additional grooves may be cut in the end faces and on the hubsinto which the rubber extends. The rubber extending into the groove onthe end faces of the hubs serves to provide an efiective seal to preventleakage between the rubber and the body of the piston and helps to holdthe rubberfrom detachment from the body. p V

The success of a piston of this character under high pressure conditionsis somewhat dependent upon the thickness of the rubber layer externallyV of the peripheries of the flanges l3. This thickness should berelatively small as compared with the diameter of the piston'so that nolarge mass of rubber will be present between the body of the piston andthe liner L on which the high pressures may become effective. Thus forexample, in a piston having an external diameter of 4 the thickness ofthe rubber between the flanges I3 and the liner L should beapproximately The rubber might be thinner or might be slightly thicker,but these proportions have proven quite satisfactory.

The flanges I3 on such a piston may .be about thick andthe grooves l2approximately 4" wide and deep. The perforations I4 on such a pistonshould be quite numerous. I find that a suitable'sizeandspacing of theseperforations on a'4 piston is to have the perforations approximately indiameter spaced from each other on centers. These perforations may beformed by drilling longitudinally of the piston through the flanges. Thedrilling may be performed through the flangesj from both ends of thepiston and it is desirable to have those perforations formed in theflanges from one end disalign'ed'orrout of registry with thoseperforations that are drilled through the flanges from the other end ofthe piston. The proportions given have proven highly satisfactory for apiston of approximately 4 in diameter. Manifestly with other sizes ofpistons the proportions may be altered accordingly.

From the above-described construction it will be appreciated that thepiston can be very easily and quickly manufactured. The bodies of thepistons. can be cast into the general shape shown and very littlemachine work other than the drilling of the perforations l4 and thereaming of bore II is required. The rubber used is of a uniformcomposition so as to bring about the desired elasticity and flexibility.In other words it is not necessary to employ two or more compositions ofrubber which when vulcanized produce hard and soft rubber on the piston.By the omission of the central flange on the body In danger of therubber becoming loosened adjacent the flange or its being chewed offadjacent the flange, and danger of scoring is entirely eliminated, andby keeping the rubber layer exteriorly of the flanges I3 relatively thinthe function of the central flange can be dispensed with entirely. 7

Various changes may be made in the details of construction withoutdeparting from the spirit or scope of the invention as defined by theappended claim.

I claim:

A mud pump piston comprising a. one-piece body having on its periphery amultiplicit of substantially equally spaced flanges of substantially thesame depth, said flanges and the spaces therebetween occupyingsubstantially the entire external surface of the body of the piston fromthe end to end thereof, rubber or the like molded around and between theflanges, the rubber forming the entire cylinder-wall engaging surfacesof the piston and externally of the flanges being relatively thin ascompared with the diameter of the piston, the flanges being perforatedwith aligned perforations and the rubber extending into the perforationsso as to be effectively anchored thereto.

ERWIN E. MILLER.

